1. Field of the Invention
This invention relates to a photoconductive member having sensitivity to electromagnetic waves such as light (herein used in a broad sense, including ultraviolet rays, visible light, infrared rays, X-rays and gamma-rays).
2. Description of the Prior Arts
Photoconductive materials which constitute photoconductive layers for image forming members for electrophotography in the field of image formation, manuscript reading devices, or solid state image pick-up devices are required to have a high sensitivity, a high SN ratio (Photocurrent (I.sub.p)/Dark current (I.sub.d)), spectral characteristics matching to those of electromagnetic waves to be irradiated, a rapid response to light, a desired dark resistance value as well as no harm to human bodies during usage. Further, in a solid state image pick-up device, it is also required that the residual image should easily be treated within a predetermined time. In particular, in case of an image forming member for electrophotography to be assembled in an electrophotographic device to be used in an office as office apparatus, the aforesaid harmless characteristic is very important.
From the standpoint as mentioned above, amorphous silicon (hereinafter referred to as "a--Si") has recently attracted attention as a photoconductive material. For example, German Laid-Open Patent Publication Nos. 2746967 and 2855718 disclose applications of a--Si for use in image forming members for electrophotography, and German Laid-Open Patent Publication No. 2933411 an application of a--Si for use in a photoconverting reading device.
However, under the present situation, while the photoconductive members having photoconductive layers constituted of a--Si have been attempted to be improved in various aspects individually including electrical, optical and photoconductive characteristics such as dark resistance value, photosensitivity and response to light, etc., and environmental characteristics during use, and further stability with lapse of time and durability, there remains room for further improvement of overall characteristics.
For instance, when applied to an image forming member for electrophotography, residual potential is frequently observed to remain during use thereof if enhancing photosensitivity and dark resistance are contemplated to be effected at the same time. When such a photoconductive member is repeatedly used for a long time, there will be caused various inconveniences such as accumulation of fatigues by repeated uses or so called ghost phenomenon wherein residual images are formed.
Further, a--Si materials may contain as constituent atoms hydrogen atoms or halogen atoms such as fluorine atoms, chlorine atoms, and the like for improving their electrical, photoconductive characteristics, boron atoms, phosphorus atoms, etc. for controlling the electroconductivity type as well as other atoms for improving other characteristics. Depending on the manner in which these constituent atoms are contained, there may sometimes be caused problems with respect to electrical, photoconductive characteristics or dielectric strength, and further durability of the layer formed.
That is, for example, when used as an image forming member for electrophotography, the life of the photocarriers generated by light irradiation in the photoconductive layer formed is insufficient, or at the dark portion, the charges injected from the support side cannot be sufficiently impeded, or there are formed defective images commonly called as "blank areas" on the images transferred to a receiving paper which may be considered to be due to the local discharge destroying phenomenon, or defective images commonly called as "white lines" which may be considered to be caused by, for example, scraping with a blade employed for cleaning. Also, when used in a highly humid atmosphere or immediately after being allowed to stand in a highly humid atmosphere for a long time, so called "faint image" is frequently observed in images obtained.
Further, when the layer thickness is as thick as ten and some microns or higher, there tends to occur such phenomena as loosening or peeling of layers off from the support surface or formation of cracks in the layers with lapse of time when allowed to stand after taking out from a vacuum deposition chamber for layer formation. These phenomena will occur particularly frequently when the support is a drum-shaped support conventionally employed in the field of electrophotography. Thus, there are problems to be solved with respect to stability with lapse of time.
Thus, it is required in designing a photoconductive material to make efforts to solve all of the problems as mentioned above along with the improvement of a--Si materials per se.
In view of the above points, the present invention contemplates the achievement obtained as a result of extensive studies made comprehensively from the standpoints of applicability and utility of a--Si as a photoconductive member for image forming members for electrophotography, solid stage image pick-up devices, reading devices, etc. It has now been found that a photoconductive member having a photoconductive layer comprising an amorphous material which is constituted of so called hydrogenated amorphous silicon, halogenated amorphous silicon or halogen-containing hydrogenated amorphous silicon which is an amorphous material containing at least one of hydrogen atom (H) and halogen atom (X) in a matrix of silicon atoms (hereinafter referred to comprehensively as a--Si(H,X)), said photoconductive member being prepared by designing so as to have a specific structure, exhibits not only practically extremely excellent characteristics but also surpasses the photoconductive members of the prior art in substantially all respects, and has especially markedly excellent characteristics as a photoconductive member for electrophotography. The present invention is based on such finding.